Since the discovery of the high-transition-temperature superconductors (HTSs), researchers have explored many methods to fabricate superconducting tunnel junctions from these materials for basic science purposes and applications. HTS circuits operating at liquid-nitrogen temperatures (∼77 K) would significantly reduce power requirements in comparison with those fabricated from conventional superconductors. The difficulty is that the superconducting coherence length is very short and anisotropic in these materials, typically ∼2 nm in the a-b plane and ∼0.2 nm along the c axis. The electrical properties of Josephson junctions are therefore sensitive to chemical variations and structural defects on atomic length scales. To make multiple uniform HTS junctions, control at the atomic level is required. In this Letter we demonstrate all-HTS Josephson superconducting tunnel junctions created by using a 500-pm-diameter focused beam of helium ions to directly write tunnel barriers into YBa2Cu3O(7-δ) (YBCO) thin films. We demonstrate the ability to control the barrier properties continuously from conducting to insulating by varying the irradiation dose. This technique could provide a reliable and reproducible pathway for scaling up quantum-mechanical circuits operating at liquid-nitrogen temperatures, as well as an avenue to conduct novel planar superconducting tunnelling studies for basic science.

The proton T 1 was measured at 132 mT in ex vivo prostate tissue specimens from radical prostatectomies of 35 patients with prostate cancer. Each patient provided two specimens. The NMR and MRI measurements involved proton repolarization, a field of typically 150 mT and detection of the 5.6-kHz signal with a superconducting quantum interference device. Values of T 1 varied from 41 to 86 ms. Subsequently, the percentages of tissue types were determined histologically. The theoretical image contrast is quantified for each case by d 5 [1 -T 1 (more cancer)/T 1 (less cancer)]. A linear fit of d versus difference in percentage cancer yields T 1 (100% cancer)/T 1 (0% cancer) 5 0.70 6 0.05 with correlation coefficient R 2 5 0.30. Two-dimensional T 1 maps for four specimens demonstrate variation within a single specimen. These results suggest that MR images with T 1 contrast established at ultra-low fields may discriminate prostate cancer from normal prostate tissue in vivo without a contrast agent. Magn Reson Med 67:1138-1145,

The condensation and evaporation of vapors of isopropanol, heptane, and cyclohexane in mesoporous silica photonic crystals are monitored by optical reflection spectroscopy as a function of sensor temperature. The spectral position of the stop band shifts to the red upon analyte adsorption, and it shifts to the blue as the sensor is heated and analyte evaporates from the porous nanostructure. The hysteresis of the optical response as the temperature of the sensor is cycled between 25 and 80 °C is characteristic of each analyte for partial pressures between 0 and 7.5 Torr. These characteristic hysteresis loops allow identification of the three analytes. The temporal response of the sensor is studied as a function of heating rate and analyte concentration in a flowing stream of analyte vapor, and it is compared with the equilibrium adsorption isotherms of the sensor. The ability of the temporal data to identify the analytes is attributed to differences in diffusion and adsorption properties of each analyte within the mesoporous silica sensor.

We have fabricated and tested two-dimensional arrays of YBa2Cu3O7−δ superconducting quantum interference devices. The arrays contain over 36 000 nano Josephson junctions fabricated from ion irradiation of YBa2Cu3O7−δ through narrow slits in a resist-mask that was patterned with electron beam lithography and reactive ion etching. Measurements of current-biased arrays in magnetic field exhibit large voltage modulations as high as 30 mV.